Dieter Wege

The synthesis of thieno[3,4-b]furan using a tandem intramolecular-reverse Diels-Alder reaction approach

Abstract The title compound has been prepared by a route involving as the key steps the intramolecular Diels-Alder addition between a furan and a pendant acetylenic ester, and the subsequent retro-Diels-Alder fragmentation of the adduct, induced by 3,6-di(pyridin-2′-yl)- s -tetrazine.

Intramolecular diels-alder reactions of benzynes application to the total synthesis of mansonone E

Abstract Substituted benzynes san be trapped intramolecularly by an attached furan moiety and such a reaction has been used in the synthesis of the naturally occurring o-naphthoquin- one mansonone E.

Novel furan derivatives related to triphenylene: benzo[1,2-c:3,4-c′:5,6-c″]-trifuran, naphtho[1,2-c:3,4-c′]difuran and phenanthro[9,10-c]furan

Abstract The title compounds have been synthesised by sequences involving as the key step the trapping of arynes with furan.

The Synthesis of Ventilone A

2-Amino-3,6-dimethoxy-4,5-methylenedioxybenzoic acid (12) was prepared from 1,4-dimethoxy-2,3-methylenedioxybenzene (8) via the isatin (11). The benzyne generated from (12) was intercepted with 3-acetyl-2-ethoxy-4-[(4-methoxyphenoxy)methyl]furan (4) to give the naphthol (27), which on treatment with cericammonium nitrate gave the dimethyl ether of ventilone A(29). Demethylation with boron tribromide then affordedventilone A (1).

The total synthesis of favelanone

Abstract (±)-Favelanone (1) has been synthesised by a sequence involving as the key step the cycloaddition of 6-methoxy-5-methyl-3-trimethylsilyloxyisobenzofuran-1-carbonitrile (3) to 7-bromo-5,5-dimethylbicyclo[4.1.0]hept-1(7)-ene (4).

Heterocyclic cycloproparenes: 5H-cycloprop[f]isobenzofuran and 5H-cyclopropa[f][2]benzothiophene

Abstract The title compounds have been prepared from the Diels - Alder adducts of 1,2-dibromocyclopropene with 3,4-bis(methylene)-tetrahydrofuran and 3,4-bis(methylene)-tetrahydrothiophene by a sequence involving dehydrogenation and dehydrobromination.

Heterocyclic cycloproparenes: Approaches to the cyclopropa[c]thiophene system

Abstract Dehydrochlorination of 6,6-dichloro-3-thiabicyclo[3.1.0]hexane generates a cyclopro, pene which can be trapped with t-BuOH or furan, while 1,5-dibromo-6,6-dimethyl-3-thiabicyclo[3.1.0]hexane undergoes dehydrobromination to afford the highly reactive 4,4-dimethyl-4H-cyclopropa[c]thiophene, which was trapped with isobenzofuran.

The synthesis of some azuleno[c]furans

Azuleno[5,6-c]furan and 4-chloroazuleno[4,5-c]furan have been prepared by a tandem cycloaddition-cycloreversion strategy. These azulenofurans are qualitatively more stable than isobenzofuran and were characterised spectroscopically and as their Diels-Alder adducts with N-methylmaleimide.

The addition of benzyne to azulene

The title reaction afforded the Diels-Alder adduct 4b,10-ethenobenz [a]azulene (4), while an analogous reaction involving 5,6-dichloroazulene gave the 6,7- and 7,8-dichloro-derivatives of (4). Treatment of (4) with 3,6-di(pyridin-2-yl)-s-tetrazine yielded benz[a]azulene.

Approaches to pseudoindene : Products derived from the carbenes benzocyclobuten-1-ylcarbene, 2-methylbenzocyclobutenylidene and o-styrylcarbene

Abstract The title carbenes, which in principle can all serve as precursors to the reactive hydrocarbon pseudoindene, have been generated by the photolysis of the sodium salts of the tosylhydrazones of (a) benzocyclobutene-1-carboxaldehyde, (b) 2-methylbenzocyclobutenone and (c) o -formylstyrene. Indene was formed in reactions (a) and (c): in the former case deuterium labelling experiments suggest a ring expansion mechanism rather than a pseudoindene intermediate. In the latter case deuterium labelling and trapping experiments implicate a symmetrical isoindene intermediate, which can arise either via pseudoindene, or via direct electrocyclic ring closure of o -styrylcarbene.